Spatial multiplexing of a wireless transmit/receive unit (WTRU) that uses multiple-input multiple-output (MIMO) communication means may involve determining a number of settings and parameters. The selection of these settings and parameters desirably improve the quality and reliability of the MIMO communications. For example it is desirable for the WTRU to determine a desired rank indicating a number of useful transmission layers.
For open-loop spatial multiplexing mode, a reported rank equal to one indicates a transmit diversity should be used for the MIMO communications, while a reported rank higher than one, (e.g., two, three, or four), indicates that large delay cyclic delay diversity (CDD) with two, three or four corresponding layers should be used.
For closed-loop spatial multiplexing mode, a reported rank indicates a closed-loop precoding with the corresponding number of layers, (e.g., one, two, three or four), should be used.
Rank measurement and generation may be performed for MIMO spatial multiplexing for both open-loop and close-loop schemes.
Additionally, the determination of a precoding matrix index (PMI) may be desirable for MIMO communications by a WTRU.
The present application includes several example methods and apparatuses for selecting and reporting ranks and PMIs for MIMO communication by a WTRU.